MSK Cortex Biochemistry

Question 1

What level of bone mineral density means someone has osteoporosis?

Answer 1

Less than 2.5 standard deviations below the mean peak value of young adults of the same race and sex

Question 2

What level of bone mineral density means someone has osteopenia?

Answer 2

Between 1 to 2.5 standard deviations below mean peak value

Question 3

What is type 1 osteoporosis?

Answer 3

Post‐Menopausal Osteoporosis with an exacerbated loss of bone in the post‐menopausal period

Question 4

What are the risk factors for type 1 osteoporosis?

Answer 4

Early menopause
Smoking
Alcohol abuse
Lack of exercise
Poor diet

Question 5

Which fractures tend to occur in people with type 1 osteoporosis?

Answer 5

Colles fractures and vertebral insufficiency fractures

Question 6

What is type 2 osteoporosis?

Answer 6

Osteoporosis of old age with a greater decline in bone mineral density than expected

Question 7

What are the risk factors for type 2 osteoporosis?

Answer 7

Similar to type 1 plus:
Chronic disease
Inactivity
Reduced sunlight exposure (Vitamin D)

Question 8

Which fractures tend to occur in people with type 2 osteoporosis?

Answer 8

Femoral neck fractures and vertebral fractures

Question 9

What can osteoporosis occur secondary to?

Answer 9

Corticosteroid use, alcohol abuse, malnutrition, chronic disease (CKD, malignancy, Rheumatoid arthritis) and endocrine disorders (Cushing’s, Hyperthyroidism, Hyperparathyroidism)

Question 10

How is osteoporosis diagnosed?

Answer 10

DEXA scan

Question 11

In osteoporosis are the levels of serum calcium and phosphate high/low/normal?

Answer 11

Normal

Question 12

What pharmacological treatments are used to try to prevent fragility fractures?

Answer 12

Calcium
Vitamin D supplements
Bisphosphonates
Desunomab
Strontium

Question 13

What is osteomalacia?

Answer 13

Abnormal softening of the bone - due to deficient mineralization of osteoid (immature bone) secondary to inadequate amounts of calcium and phosphorus

Question 14

What are symptoms of hypocalcaemia?

Answer 14

Paraesthesiae, muscle cramps, irritability, fatigue, seizures, brittle nails

Question 15

In osteomalacia what are the levels of calcium, phosphate and serum alkaline phosphatase like?

Answer 15

Calcium - low
Phosphate - low
Alkaline phosphatase - high

Question 16

What does the treatment of osteomalacia involve?

Answer 16

Vitamin D therapy with calcium and phosphate supplementation

Question 17

What can cause primary hyperparathyroidism?

Answer 17

Benign adenoma
Hyperplasia
Malignant neoplasia (rare)

Question 18

What does an overproduction of PTH result in?

Answer 18

Hypercalcaemia with subsequent symptoms and signs (fatigue, depression, bone pain, myalgia, nausea, thirst, polyuria, renal stones, osteoporosis)

Question 19

In hyperparathyroidism what are the levels of serum PTH, calcium and phosphate?

Answer 19

Serum PTH - high
Calcium - high
Phosphate - normal/low

Question 20

What is secondary hyperparathyroidism?

Answer 20

A physiological overproduction of PTH secondary to hypocalcaemia usually caused by vitamin D deficiency or CKD

Question 21

What is tertiary hyperparathyroidism?

Answer 21

Patients with chronic secondary hyperparathyroidism (usually CKD) who develop an adenoma which will continue to produce PTH despite biochemical correction

Question 22

What is Paget’s disease?

Answer 22

Chronic disorder which results in thickened, brittle and mis‐shapen bones

Question 23

What could be the aetiology of Paget’s disease?

Answer 23

Viral infection (paramyxoviruses) and genetic defects

Question 24

Why does Paget’s disease cause brittle bones which are prone to fracture?

Answer 24

Increased osteoclast activity causes an increase in osteoblast activity to counteract this however the new bone fails to remodel sufficiently and so despite it’s thickness and density the new bone is brittle and can fracture easily

Question 25

In Paget’s disease what are the levels of calcium, phosphate and alkaline phosphatase like?

Answer 25

Calcium - normal
Phosphate - normal
Alkaline phosphatase - high

Question 26

What is the treatment of Paget’s disease?

Answer 26

Bisphosphonates (which inhibit osteoclasts) or calcitonin if extensive lytic disease. Joint replacement may be necessary and pathological femoral fractures should be stabilised with long intramedullary nails or plates